Embodiments of the invention relate generally to gel and blot imaging and, more particularly, to a system and method for performing gel and blot imaging using a flat panel imaging system.
Gel electrophoresis and electroblotting are commonly used techniques for the separation and analysis of macromolecules (DNA, RNA and proteins) and the subsequent transfer of such macromolecules onto a membrane, respectively, that then enables further analysis of these macromolecules using probes, such as specific antibodies, ligands, or stains, that can and/or drive a reaction and produce a color blot (e.g., Western blot imaging and Southern blot imaging). Several detection techniques may be employed in gel and blot imaging for DNA and/or protein analysis, including the detection, recognition, and quantification of specific macromolecules in a sample of tissue homogenate or extract. Such techniques include fluorescent detection, chemiluminescent detection, and colorimetric detection. In fluorescent detection, a fluorescently labeled stain or probe is excited by light and the emission of the excitation is then detected by a photosensor (e.g., a charge coupled device (CCD) camera) that captures a digital image of the gel/blot and allows further data analysis, such as molecular weight analysis and a quantitative western blot analysis. In chemiluminescent detection, a blot is incubated with a substrate that will luminesce when exposed to a reporter on the antibody—with the light that is generated being detected by photographic film to create an image of the blot thereon or by CCD cameras to capture a digital image of the blot.
The performing of fluorescent detection, chemiluminescent detection, and/or colorimetric detection according to existing techniques—specifically with respect to the use of film emulsion and/or CCD cameras to capture images—presents some drawbacks and limitations. For example, film emulsion is the conventional detection medium for chemiluminescent detection, but is characterized by non-linear response and limited dynamic range requiring multiple exposures, thereby resulting in a time-consuming and expensive imaging procedure. As another example, as chemiluminescent signals generated from the blots are normally weak and time-varying, relatively fast exposure (e.g., on the order of a minute), low noise, and high light detection efficiency is required for accurate image capture when using CCDs. Thus, limitations of the CCDs regarding operation at a low frame rate (due to the inherent sequential read-out thereof) and low temperature (to achieve a reasonable noise level) present challenges in accurately capturing the chemiluminescent signals. Still further, CCDs require a high efficiency optical lens to focus the large blot to small CCD chips (˜1 cm2)—with the optical lens adding to the cost of the high-end CCDs, increasing the size and vertical space of the imaging device (due to the large working distance of the CCD camera), and also causing problems with regard to light collection efficiency (due to the large working distance). Yet still another drawback of image capture via CCD is that the capturing of images can take approximately 3-20 minutes—depending on the desired exposure.
Other more recent attempts to provide a system that captures a digital image of the blot include a C-digit system released by LICOR Biosciences that utilizes a linear scanner with sixteen linear sensors. The linear scanner combines short working distance (like film emulsion) to maximize light collection efficiency and multiple small low cost linear sensor arrays to meet the data acquisition time requirement, but the scan time to scan the large area is still around multiple minutes per pass (i.e., 6-12 minutes). Additionally, there is a concern that during the scanning time (on order of 10 minutes), the transient behavior of the chemiluminescence in the blot itself will be changing. As such—as the linear scan is happening—the intensity at the beginning of the scan will be higher than the intensity of at the end of the scan (bottom of the scan), therefore introducing an artificial gradient in the measurement.
Therefore, it would be desirable to provide a system and method for image acquisition in gel and blot imaging that overcomes the aforementioned drawbacks of conventional imaging techniques and associated systems. It would also be desirable for such systems and methods to provide improved performance in regards to sensitivity, dynamic range, exposure time, and quantum efficiency, while eliminating costly high-efficiency imaging optics such as are used with existing CCD image sensors, so as to provide a system at a reduced cost and size.